Abstract 4045: DCC-3084, a RAF dimer inhibitor, broadly inhibits BRAF class I, II, III, BRAF fusions, and RAS-driven solid tumors leading to tumor regression in preclinical models

Background: Mutations in the RAS/MAPK pathway are a frequent driver of cancer, with oncogenic RAS or RAF mutations occurring in >30% of all cancers. First generation BRAF inhibitors are approved for use for tumors with Class I BRAF mutations (V600X). However, these drugs are not efficacious in RAF dimer mutant and RAS mutant cancers due to paradoxical activation of RAF dimers. Herein, we describe DCC-3084, a potent and selective investigational Switch Control inhibitor of BRAF and CRAF kinase dimers that targets Class I, II and III BRAF mutations, BRAF fusions, and BRAF/CRAF heterodimers. DCC-3084 combines with inhibitors of additional nodes in the MAPK pathway to potentially target a large unmet medical need in RAS and RAF mutant cancers.

Methods: Inhibition of RAF kinases, including off-rate analysis, was measured using recombinant enzymes. X-ray crystallography was used for structure-based drug design. Cellular proliferation was measured using resazurin to monitor cell viability. Synergy in cells was measured using BLISS scores and curve shift analysis. Inhibition of ERK or RSK phosphorylation was measured by AlphaLISA or ELISA. Pharmacokinetics (PK) in the plasma, brain and CSF compartments were measured following oral dosing in Wistar rats. RAF and RAS mutant mouse xenograft models were used to assess PK, pharmacodynamics (PD), and efficacy.

Results: DCC-3084 is a potent and selective Switch Control inhibitor of RAF dimers that was designed to target Class I, II, III BRAF mutants, BRAF fusions, and BRAF/CRAF heterodimers. DCC-3084 inhibits BRAF and CRAF, exhibiting slow off-rates (t1/2 >20 hr). Potent single-agent inhibition of MAPK pathway signaling and cellular proliferation was observed in a wide range of Class I, II, III BRAF and BRAF fusion altered cell lines. Synergy was observed in combination with inhibitors of other nodes in the RAS/MAPK pathway in RAS mutant cell lines. DCC-3084 was demonstrated to be CNS penetrable and exhibited dose dependent oral exposure with robust inhibition of the RAS/MAPK pathway in PK/PD models. DCC-3084 accumulated in tumor tissue relative to plasma, further demonstrating a favorable pharmaceutical profile. Oral treatment of DCC-3084 as a single agent resulted in tumor regression in BRAF mutant and KRAS Q61K mutant mouse xenograft models and tumor growth inhibition in KRAS G12C/D mutant models. Additionally, DCC-3084 in combination with a MEKi resulted in tumor regression in KRAS mutant models.

Conclusions: The Switch Control inhibitor DCC-3084 broadly inhibits Class I, II and III BRAF mutations, BRAF fusions, and BRAF/CRAF heterodimers leading to tumor regression in preclinical models. The overall preclinical profile of DCC-3084 supports IND-enabling activities towards clinical development in a key area of unmet medical need in RAS and RAF mutant cancers.

Citation Format: Stacie L. Bulfer, Bertrand Le Bourdonnec, Jeffery D. Zwicker, Yu Mi Ahn, Gada Al-Ani, Hikmat Al-Hashimi, Chase Crawley, Kristin M. Elliott, Saqib Faisal, Andrew M. Harned, Cale L. Heiniger, Molly M. Hood, Salim Javed, Michael Kennedy, Joshua W. Large, Cynthia B. Leary, Wei-Ping Lu, Kylie Luther, Max D. Petty, Hunter R. Picard, Justin T. Proto, Yeni K. Romero, Forrest A. Stanley, Kristen L. Stoltz, Daniel C. Tanner, Hanumaiah Telikepalli, Mary J. Timson, Lakshminarayana Vogeti, Subha Vogeti, Sihyung Yang, Lexy H. Zhong, Bryan D. Smith, Daniel L. Flynn. DCC-3084, a RAF dimer inhibitor, broadly inhibits BRAF class I, II, III, BRAF fusions, and RAS-driven solid tumors leading to tumor regression in preclinical models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4045.

Abstract B129: Preclinical studies with DCC-3116, an ULK kinase inhibitor designed to inhibit autophagy as a potential strategy to address mutant RAS cancers

Background: Cancer cells activate autophagy, a catabolic process to resupply nutrients and recycle damaged organelles, in order to survive stresses such as limited nutrients and hypoxia, or chemotherapy treatments. RAS mutant cancers, in particular, have been found to require autophagy for tumor growth and survival.1,2 Treating RAS mutant tumors with inhibitors of the downstream MAPK pathway has been largely unsuccessful, as these drugs have been shown to further stimulate autophagy, allowing for tumor cell survival.3,4 Inhibiting autophagy in combination with MAPK pathway inhibition may represent a possible new treatment paradigm for RAS mutant cancers. Proof-of-concept for this strategy was obtained in cancer models and in a RAS mutant pancreatic cancer patient by blocking autophagy with derivatives of chloroquine, in combination with MAPK inhibitors.3,4 Chloroquines indirectly block autophagy via disruption of lysosomal function, which may also affect important normal cellular processes. Chloroquines accumulate in tissues, notably the brain, where autophagy may be vital for neuronal health. The potential exists to more selectively inhibit autophagy by targeting specific components of the autophagy pathway. ULK1/2 kinases initiate autophagy and provide the potential for a targeted approach for selectively inhibiting autophagy in RAS mutant cancers. Herein, we describe preclinical studies with the ULK inhibitor DCC-3116, designed as a potential inhibitor of autophagy in RAS mutant cancers. Methods: In vitro kinase assays were performed using cellular levels of ATP (1 mM) and a peptide substrate. In cell assays, ULK activity was assessed using an ELISA for phosphorylated ATG13. Autophagosome formation was measured using the dye, Cyto-ID. Autophagic flux was assessed using cells expressing the autophagy protein LC3 fused to luciferase. The synergy of DCC-3116 in combination with MAPK inhibitors was assessed in 2D or 3D cell growth assays. Xenograft models were used to assess pharmacokinetics (PK) and pharmacodynamics (PD), as well as efficacy in vivo. Results: DCC-3116 is a potent and selective inhibitor of ULK1/2, inhibiting no other kinases within 30-fold of ULK potency, and only 5 kinases within 100-fold. DCC-3116 inhibited phosphorylation of the ULK substrate ATG13 in cancer cell assays. DCC-3116 inhibited autophagosome formation, as well as degradation of the autophagy marker LC3. DCC-3116 exhibited synergy in vitro in combination with MAPK pathway inhibitors in inhibiting cancer cell growth. In PK/PD models, oral doses of DCC-3116 led to sustained inhibition of ATG13 phosphorylation. DCC-3116, in combination with MAPK inhibitors, exhibited additivity or synergy in inhibiting tumor growth in xenograft models. DCC-3116 exhibited low brain penetration in rats, minimizing inhibition of CNS autophagy. Conclusion: Selectively blocking autophagy via inhibition of ULK kinases, in combination with MAPK pathway inhibition, is a promising therapeutic approach for RAS mutant cancers. DCC-3116 warrants further study as an inhibitor of autophagy, and has been selected as a candidate for potential development in the treatment of RAS mutant cancers.

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Citation Format: Bryan D Smith, Lakshminarayana Vogeti, Anu Gupta, Jarnail Singh, Gada Al-Ani, Stacie L Bulfer, Timothy M Caldwell, Mary J Timson, Subha Vogeti, Yu Mi Ahn, Hikmat Al-Hashimi, Chase K Crawley, Cale L Heiniger, Cynthia B Leary, Justin T Proto, Quanrong Shen, Hanumaiah Telikepalli, Karen Yates, Wei-Ping Lu, Daniel L Flynn. Preclinical studies with DCC-3116, an ULK kinase inhibitor designed to inhibit autophagy as a potential strategy to address mutant RAS cancers [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B129. doi:10.1158/1535-7163.TARG-19-B129